When you returned to Thailand, the immigration officer will stamping the visa arrival on your passport and your departure card and then return to you.
Please see attached sample.
90 day report must be made within 15 days before or after 7 days the period of 90 days expires.
If you leaves Thailand and re-enters, the day count starts at 1 in every case.
If you plan to go Japan on 3 Sep’15. This time No need to apply 90 day report.