There are two popular types of processing visa approval letter (used for visa on arrival): normal processing and urgent processing.

Normal processing is the normal time for the visa approval letter to be issued by the Immigration, which is within 2 working days, and the visa approval fee is from US19.5$ for this type of processing. Similarly, urgent processing is the urgent time for this approval letter to be issued, which is only 1 working day, and the fee = normal processing fee + US10$.