Will I receive another 60 days upon re-entering Thailand with a re-entry visa after extending my tourist visa?

If you have extended your 60-day tourist visa by an additional 30 days and then leave Thailand, a re-entry visa will only keep your original stamp active; it will not grant you another 60 days upon re-entry. For a new 60-day stay, you would need to apply for a new tourist visa at a Thai embassy. A simple border crossing would give you an additional 30 days, which can also be extended by 30 days.