Do I need to show an onward ticket when arriving in Thailand on a single-entry 90-day Non-O volunteer visa?

Hello All,

We will be arriving on single-entry 90-day Non-O (volunteer visas). Although the embassy recognizes the intention is to stay much longer than this, Canada only offers single-90 Non-O visas and then you are to extend in country (after getting work permit). Anyways, my question is whether we will be required to show an onward ticket that leaves before the 90 days are up? Thanks.