SINGAPORE - Indonesia is buying submarines from South Korea and coastal radar systems from China and the United States. Vietnam is getting submarines and combat jets from Russia, while Singapore - the world's fifth-largest weapons importer - is adding to its sophisticated arsenal.
Wary of China and flush with economic success, Southeast Asia is ramping up spending on military hardware to protect the shipping lanes, ports and maritime boundaries that are vital to the flow of exports and energy.
Territorial disputes in the South China Sea, fuelled by the promise of rich oil and gas deposits, have prompted Vietnam, Malaysia, the Philippines and Brunei to try to offset China's growing naval power.
Even for those away from that fray, maritime security has been a major focus for Indonesia, Thailand and Singapore.
"Economic development is pushing them to spend money on defence to protect their investments, sea lanes and exclusive economic zones," said James Hardy, Asia Pacific editor of IHS Jane's Defence Weekly. "The biggest trend is in coastal and maritime surveillance and patrol."
As Southeast Asia's economies boomed, defence spending grew 42 percent in real terms from 2002 to 2011, data from the Stockholm International Peace Research Institute (SIPRI) shows.
High on the list are warships, patrol boats, radar systems and combat planes, along with submarines and anti-ship missiles that are particularly effective in denying access to sea lanes.
"Submarines are a big thing," said Tim Huxley, executive director for Asia at the International Institute for Strategic Studies. "They can do immense damage without being seen, without being anticipated, and they can do that anywhere in the region."
For decades, much of Southeast Asia spent little on weapons other than guns and small tanks. Most threats were internal and the umbrella of U.S. protection was deemed enough to ward off any potential aggression from overseas.
With China's growing muscle and more funds available, the shopping lists are getting more sophisticated. Most countries in the region are littoral, so the emphasis is on sea and air-based defence.
Malaysia has two Scorpene submarines and Vietnam is buying six Kilo-class submarines from Russia. Thailand also plans to buy submarines and its Gripen warplanes from Sweden's Saab AB will eventually be fitted with Saab's RBS-15F anti-ship missiles, IISS says.
Singapore has invested in F-15SG combat jets from Boeing Co in the United States and two Archer-class submarines from Sweden to supplement the four Challenger submarines and powerful surface navy and air force it already has.
Indonesia, a vast nation of islands with key sea lanes and 54,700 km (34,000 miles) of coastline, has two submarines now and ordered three new ones from South Korea. It is also working with Chinese firms on manufacturing C-705 and C-802 anti-ship missiles after test-firing a Russian-built Yakhont anti-ship missile in 2011.
While it is not an arms race, analysts say, the build-up is being driven by events in the South China Sea, long-standing squabbles between neighbours and a desire to modernise while governments have the money.
Piracy, illegal fishing, smuggling, terrorism and disaster relief also play their parts, along with keeping the influential military happy in places such as Thailand and Indonesia.
There is a "general sense of strategic uncertainty in the region" given China's rise and doubts about the U.S. ability to sustain a military presence in Asia, said Ian Storey, a senior fellow at the Institute of Southeast Asian Studies.
"Southeast Asian countries will never be able to match China's defence modernisation," he said, citing Vietnam's push for a deterrent. "If the Chinese did attack the Vietnamese, at least the Vietnamese could inflict some serious damage."
SIPRI says Indonesia, Vietnam, Cambodia and Thailand took the lead in boosting their defence budgets by between 66 and 82 percent from 2002 to 2011.
But the region's biggest spender with the best-equipped military is Singapore, a tiny island that is home to the world's second-busiest container port, a global financial centre and a major hub for oil, gas and petrochemicals.
The wealthy city-state, along with Malaysia and Indonesia, sits on the Strait of Malacca that links the Pacific and Indian oceans. A teeming shipping route, the strait is also a narrow "choke point" with huge strategic implications for the energy, raw materials and finished goods flowing east and west.
At $9.66 billion, Singapore's 2011 defence budget dwarfed Thailand's $5.52 billion, Indonesia's $5.42 billion, Malaysia's $4.54 billion and Vietnam's $2.66 billion, IISS says.
The situation is far less intense than in North Asia where China, Japan, the United States, Russia and the two Koreas are involved. But Southeast Asia seems to be following the trend of pursuing military systems that can be used offensively.
"It's an indefinite process," said Huxley at IISS. "Governments are likely to go on devoting resources - that are increasing in real terms - to defence and military modernisation."
Official data on the amount and purpose of the spending is often opaque - how much goes to boots, bullets and salaries and how much to advanced hardware that can project power?
The defence spending figures also may not tell the full story. Countries such as Vietnam and Indonesia have used credit arrangements or the sale of energy exploration rights in the past to fund arms imports that did not appear in the defence budget, analysts say.
"Vietnam has stopped reporting defence and security budgets as part of its budget reporting, leaving a suspicious gap between total budgeted expenditure and the sum of the reported spending areas," said Samuel Perlo-Freeman, director of SIPRI's Military Expenditure and Arms Production Programme.
Buying and building
With defence budgets in many Western nations under pressure, Asia is attractive for makers of weapons, communications gear and surveillance systems. Lockheed Martin and Boeing's defence division both expect the Asia-Pacific region to contribute about 40 percent of international revenues.
"The maritime environment in the Pacific has everybody's attention," Jeff Kohler, a vice president at Boeing Defence, said at the Singapore Airshow in February.
Vietnam got 97 percent of its major weapons - including frigates, combat planes and Bastion coastal missile systems - from Russia in 2007-11 but is looking to diversify by talking to the Netherlands and the United States, SIPRI says.
The Philippines, which relies on the United States for 90 percent of its weapons, plans $1.8 billion in upgrades over five years as it sees a growing threat from China over the South China Sea squabble.
The focus is on the country's naval and air forces that analyst Sam Bateman sees as "rather deficient".
"The particular requirement of the Philippines is air surveillance," said Bateman, principal research fellow at the Australian National Centre for Ocean Resources and Security.
Anti-submarine capabilities are a priority, a Philippine defence department planner told Reuters.
Thailand, whose military has staged 18 successful or attempted coups since 1932, has built a patrol vessel designed by Britain's BAE Systems. It plans to modernise one frigate and, within five years, buy the first of two new ones.
"We are not saying these will replace submarines but we are hoping that they can be equally valuable to Thailand," defence ministry spokesman Thanathip Sawangsaeng told Reuters.
Singapore buys mostly from the United States, France and Germany but also has its own defence industry, centred on ST Engineering. The state-owned group supplies the Singapore Armed Forces and has many customers abroad.
"Most countries are either interested in or actively pursuing their own domestic arms industry," said Storey.
"It's cheaper than buying from overseas, long-term they're looking at developing their own export markets and, certainly this is true for Indonesia, it insulates them from sanctions from countries like the United States."