What is the ruling on a seller who withdraws from selling a tuk-tuk vehicle after reaching an agreement with the buyer and the buyer preparing the money, and what are the consequences for both the seller and the buyer in this situation?

If what transpired between the two parties was merely a promise, then the seller is not obligated to pay any financial compensation to the promisee for backing out of the sale, unless the promisee incurred actual damage due to this withdrawal and bore a cost. In that case, the promisor is obligated to compensate them for the actual damage, because a promise becomes legally binding if it results in a cost to the promisee, unless there is a valid excuse for the promisor.