True Move has just released the official prices of iPhone 5 in Thailand. You can reserve the device on their website now. No news yet from AIS and DTAC.
iPhone 5 with no contract:
16GB 24,550B, 32GB 28,250 & 64GB 31,950B
iPhone with contract:
16GB 23,677B, 32GB 27,283B & 30,807B
Prices already include VAT