Before you sign a sales agreement you should always allow a property lawyer in Thailand look over the document to ensure that your interests are covered. There are certain issues that would need to be covered and at times the developer might leave these out such as building timelines when buying offplan. This is a very basic overview of the sales agreement and you need to seek proper legal advice if you are buying property. The rights, duties, and responsibilities of all needs to be covered.
There needs to be a timeline when buying pre-construction as the developer could very well keep extending it. There needs to be penalties for late completion as well as a payment schedule at each stage of the development. This protects you where you give a large deposit and the project is never started. This provides a smaller risk to your money if things go wrong. They would normally divide the project into stages and at each stage they would expect your next payment. Check the timeline for these.
You will need to prove to the government that you have brought in the money from outside of Thailand. For this you are going to need to have a Foreign Exchange Certificate I order to show that the money came from abroad. This is what the government wants to see that money was brought into Thailand and that Thai Baht was then used to buy the property. The foreign exchange must be made in a local Thai bank so you will need to speak to a property lawyer as to how this normally gets done in Thailand. Much like penalties on the developer not performing you need to check if there is a penalty if you also pay late. Also note that normally you cannot get your deposit back in Thailand unless there is a case for damages with regards to the developer where there is non-delivery or where the developer is in default and this is why due diligence is needed.
Going to court with a litigation case can be costly. It is always best to add a clause in for arbitration in the event of a problem. This cuts down on cost and allows people to come to a settlement that does not create a bigger problem. People prefer to have arbitration than litigation when it comes to property problems or failures if there are any. Again this would be in the sale agreement for the property.
You need to ensure that what is in your sales agreement is what you are getting. This comes down to size as normally in Thailand they will use meters as a form of measurement. When the property is for the international market. There are also Thai measurements and you can have an attorney convert these for you. You will need to check that your measurements are correct as there can be misunderstandings. If it says the room is 4meters wide is that the internal measurements or the external measurements. These are things you have to ask about as these types of problems do occur.
Always seek property legal and tax advice in Thailand. This and the sales agreements ti ensure that you understand what is written in the agreement. If you are dealing with a large well-known developer then your risk is lower as they have a reputation to protect.