Congratulations! You aced the interview with Owen Oil Tools LP, Thailand branch. You have been offered a job and have discussed all the particulars. Now you need to put it in writing.
Even if the interviewers tell you a formal job offer is in the mail, it is still a good idea for you to write your own letter thanking the company for the position, expressing your enthusiasm about working there, and outlining the details of employment as you understand them. It will often take the company a few days to compile your offer letter; you can put together a quick letter and send it immediately. Then, should any discrepancies in the understanding of the terms occur, you will be able to discuss these immediately before you sign the formal acceptance letter or agreement.