Last year, the National Legislative Assembly proposed a $7 billion defence budget for 2019, a $1 billion increase since the latest 2014 coup.
But Pheu Thai, which supports ex-premier Thaksin Shinawatra and the country's most popular political party, has vowed to end conscription and cut spending by 10 percent if it beats the odds and returns to power after the March 24 poll.
PM Prayut told reporters that the increase in the defence budget is necessary to upgrade obsolete gear.
The military conscription, he added, is "a duty of all Thai men". The army runs an annual draft for 100,000 men each year - all male citizens must participate at least once after they turn 21, but are exempted if they are students.
The general election is scheduled to take place on March 24, marking it first since the coup in 2014.
Incumbent PM Prayut Chan-o-cha has been the most popular choice for the premiership in the next general election, according to a recent poll conducted by the National Institute of Development Administration (NIDA).