Reference to your query regarding 39 categories of prohibited businesses, the advice has received as follows:

Actually, it is a list of 39 occupations that prohibited to foreigners. It means only Thai Citizens are able to work in these 39 occupations.

1. Labouring work
2. Work in agriculture, animal husbandry, forestry or fisheries excluding specialized work in each particular branch or farm supervision
3. Bricklaying, carpentry or other construction work
4. Wood carving
5. Driving mechanically propelled vehicles or driving non-mechanically-propelled vehicles, excluding piloting of international aircraft
6. Shop assistant
7. Auctioneer
8. Supervising, auditing or giving service in accountancy excluding occasional internal auditing
9. Cutting or polishing jewelry
10. Haircutting, hairdressing or beauty treatment
11. Cloth weaving by hand
12. Weaving of mats or making products from reeds, rattan, hemp, straw or bamboo
13. Making of rice paper by hand
14. Lacquerware making
15. Making of Thai musical instruments
16. Nielloware making
17. Making of products from gold, silver or gold-copper alloy
18. Bronzeware making
19. Making of Thai dolls
20. . Making of mattresses or quilt blankets
21. Alms bowl casting
22. Making of silk products by hand
23. Casting of Buddha images
24. Knife making
25. Making of paper or cloth umbrellas
26. Shoemaking
27. Hat making
28. Brokerage or agency, excluding brokerage or agency in international trade
29. Engineering work in civil engineering concerning design and calculation, organization, research, planning, testing, construction supervision or advice, excluding specialized work
30. Architectural work concerning design, drawing of plans, estimating, construction supervision or advice
31. Garment making
32. Making pottery or ceramics
33. Cigarette making by hand
34. Tour guide or conducting sightseeing tours
35. Street vending
36. Typesetting of Thai characters by hand
37. Drawing and twisting silk-thread by hand
38. Office or secretarial work
39. Legal or litigation services