When you travel across several time zones,the body clock will not correspond with the destination time,so it experiences daylight and darkness in conflict with its previously established rhythm.For example,if you travel from Thailand to the U.S.,where (on the East Coast of the US)there is a 12-hour time difference,your body,previously set to Thailand time,will think that if is still 11 AM,though the local time in the U.S.is 11 PM.
Consequently,you may find zones(such as traveling from Thailand to Japan)typically does not cause jet lag.