I think it would be a great idea for you to read posts from the last few weeks to understand what is needed and has been successful to apply for the DTV.
I'm quite sure I saw a steady caravan of cars, trucks, scooters and elephants carrying household goods since the DTV visas were announced 3 months ago heading from Malaysia to the Thai border.
a work contract is an offer of employment generally stating the agreement, the employment certificate states that your employment is current and the duties regarding remote work are necessary.
What defines employment is giving the embassy whatever piece of paper they want, and many seem to like this one.
Take a bus to Pattaya in the morning, visit agent, have your bank account by afternoon. I recommend Tik Tok Services, they will pick you up and drop you off. Very good take care.