Surayud Chulanont, the former general appointed prime minister after the coup, gave no reason for the hike in military spending except a passing allusion to the three-year uprising in the Muslim-majority south.
He said the government would "raise the efficiency of intelligence and operations" and "integrate efforts of resolving security problems in border provinces in the south to boost public trust in government security enforcement".
"They've suffered as an institution financially and now they are making up for lost time"
Thitinan Pongsudhirak, Chulalongkorn University
Abhist Vejajiva, head of the former opposition Democrat party, said the military "should be careful because this raises suspicions".
In addition to the budget, the Council for National Security, as the coup leaders call themselves, is also under public scrutiny for other scandals.
Thitinan Pongsudhirak, a political analyst from Chulalongkorn University, said the military "was in disgrace" throughout the 1990s.
"They've suffered as an institution financially and now they are making up for lost time," said Thitinan.
Others said the armed forces could even be building up a war-chest for a run at politics after elections scheduled for November or December.
"The military and the government it appointed should know there is strong suspicion across the country that the generals are padding the military budget for no other reason than because they can," the Bangkok Post said in a recent editorial.
"There are many unanswered questions about whether the military is making essential purchases or acquiring more means to cling to power."
Anti-coup campaigners were also furious over a clause in the new constitution being drawn up by an army-appointed council that says the army has a right to receive adequate "military forces, weapons, ammunition, military equipment and technology".
Analysts warn that the combination of scandals, constitution and budget could eventually crystallise serious opposition to army rule, as happened in 1991-92.
"There's no immediate moral outrage, but I think that it is creeping in," Thitinan added. "This sort of thing is certainly raising the stakes for the army because long term they are generating more and more opponents."