You should definitely get any contract checked by a property lawyer.
There is no legal requirement for a lawyer when buying a property in Thailand. However, a lawyer can make the process smoother and ensure you get what you want without any issues.
The main reason a lawyer is highly recommended is that the process is not regulated, with individuals falling prey to scams.
Your independent lawyer will work to ensure your interests are met
Let me know if you need a good lawyer, I know a couple.