If you do come in visa exempt, check with your airline on the requirement for a return or onward flight. Some airlines enforce that tightly. If you search this forum, you can see various tips on addressing this through cheap throw-away tickets or refundable that can be cancelled once you are in-country without penalty. The airline would want to see the onward/return portion within 29 days if doing a visa exempt (my experience with ANA airline was that they don't understand (maybe, don't care) about extension from there or any intention to switch to another visa, they wanted to see withing the 29 days of arrival (the 30 day clock starts on arrival day)).