If you're coming from California, sail Southwest-ward. Cross the Pacific Ocean. Pass Hawaii, Marshall Islands, Marianas Islands, and you will reach the Philippines. From Philippines sail farther westward, or pass between Taiwan and Northern Philippines, sail along Vietnamese Coast and you will reach the Gulf of Thailand. Going back, sail opposite course of your track, the way you came from. It would take about 22-25 days to travel from San Diego to Manila, Philippines on good speed of 14-18 knots depending on your route. Another 4-5 days from Philippines to Gulf of Thailand. If you don't have your own boat try to contact a company in shipping business who would take a passenger en route. Unfortunately, there are quite a few so if you wanna do this, rent your own boat. But it will cost a fortune.