What should I do if I'm unable to submit my 90-day report online in Thailand?

I am having the same problem. I am inside of the 15 day early reporting window. I guess I will be going to CNX Immigration tomorrow.

Also worth trying to leave the "Flight No" field in the travel information section blank.

In addition to all the above, did you get a new passport / new extension / new tm 30 in the meantime? Those could also be reasons why it doesn't work.

If the 90 day online report system does not work, AND you’re between the due date and 15 days prior to the due date, AND you already filed one 90 day report in person, there are some troubleshooting techniques you can use to try and get the system to work for you.

1. Make sure you’re filling in the information, and only the information, requested.

2. Make sure you are keying in the date and month correctly

3. Turn off any pop-up blockers

4. Turn off any auto-translate

5. Turn off any VPNs (Virtual Private Networks) that you may be using - including any data saving applications

6. If you’re using one of the applications, use the web-based system

7. If you’re using the web based system, try using a different browser and clear the cache.

8. Make sure your web browser isn’t automatically filling in the forms.

9. Make sure you aren’t confusing “O”(Oh) with “0” (zero)

10. If you’re keying your date manually, try using the drop-down date selection box

If the system still doesn’t work, then you may need to file it in person.

Have you done steps 1 through 9?