Thailand
Also known as the Royal Thai Armed Forces, they are headed directly by the King of the state. Having participated throughout numerous wars in history, most of them based within South East Asia, this military only has about 360K active personnel. At the same time, about 200K people are in reserve.
Even though the country is not very big, it had a budget of about $7.1 billion in 2021 for its forces. After considering that the state is mainly made up of numerous islands, it does employ much of it in its navy and air force. The country also has mandated conscription at the age of 21.