Which location is known for receiving rough gemstones from Mong Hsu into Thailand?

Mae Sai is recognized as a key entry point for rough gemstones from Mong Hsu in Myanmar into Thailand. This border town is strategically located near the Shan State of Myanmar, where significant deposits of high-quality rubies are found. The gemstones, particularly rubies, are often transported from Mong Hsu through Mae Sai due to its geographical proximity, making it a central hub for the trade of these precious stones.

Mae Sot, while also a border town, is historically less associated with the specific trade routes for Mong Hsu gemstones compared to Mae Sai. Phuket and Bangkok, although important cities in Thailand, do not serve as primary entry points for the influx of rough gemstones from Myanmar. Instead, Bangkok is more involved in trading and market activities once the gemstones arrive and are distributed further in Thailand and internationally. Therefore, the prominence of Mae Sai in this context makes it the correct answer.