Yes, you can. You should be stamped in for 45 days on your first arrival (as it is after October 1, the date the permission to stay changes from 30 to 45 days). You should be stamped in for 45 days on your second arrival. If necessary (I don't see the day you arrive in Thailand the second time, from Vietnam), you can obtain an additional 30-day extension of stay from immigration for 1,900 baht. Documentation needed is at:
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