Import Duty Exemption For Non-Immigrant Visa *Is there exemption for personal/household items?You have to have a job and work permit and be on a 1 year extension of stay.
1.Nonresidents resuming residents in Thailand must be granted a non-immigrant quota as shown in a passport or a Nonresident Identification Card; or
2.Nonresidents granted to work in Thailand will be regarded as resuming residents in Thailand provided they have a one-year non-immigrant visa issued by the Immigration Department. In case where the non-immigrant visa has not yet been granted, either of the following documents may be accepted:
Source/Read more here:http://www.customs.go.th/Customs-Eng/HouseholdEffects/HouseholdEffects.jsp?menuNme=HouseHold