Are you a US Citizen - thus subject to US taxes?
How many hours per week? If the destination normally works 50-hours per week, you will work at least 50-hours thus spread that $4k on that basis. Are you paid overtime over the local base hours - and at what rate?
Are the accommodations taxed as income? Probably if located in a town. Perhaps not if it is a remote construction camp. However, the latter case may be taxed unless single status.
Is a car furnished? Is it taxed as income?
How much leave, when, paid to where-point or origin instead of Thailand?
What kind of storage provided at home, what kind of shipment alloted for overseas, and back?
Is communication home to family available via free satellite link or via phone cards?
What destination? Some overseas places (Iraq) require better uplift than other places (Aruba).
Do you need experience that you will get at this site? Will this be a great opportunity for some reason besides pay?
Do you get paid holidays?
How does the rate compare to your rate at home?
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John