How can I navigate my DTV application process while dealing with a trip to Japan and potential re-entry issues?

I plan to apply for DTV soft power with a muay Thai training. They ask I select a start date for the training. Situation is a bit complicated. I am currently in Thailand and will leave to do the DTV. I need to go to Japan for two months but because of my nationality I am not eligible to apply for visa except by going back home and applying through Japan embassy there in person or having a dtv visa and applying in Thailand in person.

This means, I need tk get my dtv, my first 180 entry will be very short, maybe a week which is the Japan visa processing time then I'll be gone for two months or two and half then back for the training.

How can i approach this situation? Will I face issues in my Re entry?