The answer to this question depends if you are purchasing from a developer or a private owner.
When purchasing from a developer, a reservation deposit is first required to officially remove the unit from the market. This is typically about 100,000-200,00 THB or 1-2% of total purchase price.
You will then have 30 days after the reservation, to review the sales and purchase agreement and finalize any commercial agreement with the developer prior to entering into payment instalments.
That is an example of a Payment Structure:
Reservation Deposit (1st payment) = 2%
Sign contract within 30 days (2nd payment) = 23%
Finish foundation post (3rd payment) = 15%
Finish concrete structure (4th payment) = 20%
Finish walls and roof tiles (5th payment) = 15%
Finish floor finishing and interior (6th payment) = 15%
Property Transfer / Land Registration (7th payment) = 10%
Tip: Instalments should be based on build milestones and not fixed dates. This ensures that progress in the build is being made before more capital is laid out.
When purchasing from a private seller a reservation deposit (typically 5-10% of the purchase price) is paid to a lawyer or Fazwaz's client account. In the event that the reservation deposit is non-refundable (typical in Bangkok) this is paid directly to the seller.
If the buyer is conducting a legal due diligence on the property (deposit refundable subject to completion) then all property documents will be handed to solicitors to review and draft a sales and purchase agreement. This will typically take 4-6 weeks but the process can be sped up or slowed down based on the requirements of the buyer and seller.
With both parties ready to proceed the balance of the full purchase price (less the 5-10% reservation deposit) is either prepared in a cashiers cheque (for execution at the land department) or a POA is given to a legal representative that will execute the transfer on your behalf.
You are not required as the buyer or seller to be present in Thailand to execute the transfer of a property. A power of attorney can be given to your FazWaz agent or solicitor to execute settlement on your behalf at the land department.