The question is asking about a military coup that took place in the latter half of the year 2006.

Option 1, Cambodia, is incorrect because there was no military coup in Cambodia during 2006.

Option 2, Laos, is not correct for the same reason. No documented military coups occurred in Laos in this period.

Option 3, Thailand, is the correct answer. On 19 September 2006, a military coup occurred in Thailand. The Royal Thai Army staged the coup against the elected caretaker government of Prime Minister Thaksin Shinawatra.

Option 4, Vietnam, is also incorrect. Vietnam did not experience a military coup in 2006.

To summarize, a military coup took place in Thailand, not in Cambodia, Laos or Vietnam in the latter half of 2006. Therefore, the third option is the correct answer.