Will I be denied entry?

It happens if you've been in the country too long. If you stay 170 days out of 180, immigration will likely pull you aside. Always have a backup plan to fly to a different country entirely.

Is a land border better than a flight?

No. Flights are generally safer for your entry record. Land borders are prone to 'unofficial fees' and stricter scrutiny regarding how you support yourself.

Staying in Southeast Asia longer: How to do a visa run

A visa run involves exiting a country and re-entering to reset your tourist stamp or visa validity. You must check the specific 'days per year' limits for your destination, as most countries like Thailand and Indonesia have strict caps on back-to-back entries.

Check your visa-exempt rules. Research the exact number of visa-free days allowed for your passport. Do not assume you get the same amount of time upon re-entry; some countries limit you to 90 days total within any 180-day period.
Choose your border crossing. Flying is generally more reliable than land borders. Land border agents have more discretion to deny entry if they suspect you are living in the country illegally. Always have a printed flight out of the country.
Prepare your 'onward travel' proof. Immigration will often ask for an exit flight. Do not risk a fake booking; use a service like 'Onward Ticket' to rent a legitimate, verifiable flight reservation for 24-48 hours.
Carry hard cash. Bring at least $300-$500 USD in crisp, clean bills. Some borders legally require proof of 'sufficient funds' to enter, and having cash on hand often prevents unnecessary questioning.

Will I be denied entry?: It happens if you've been in the country too long. If you stay 170 days out of 180, immigration will likely pull you aside. Always have a backup plan to fly to a different country entirely.
Is a land border better than a flight?: No. Flights are generally safer for your entry record. Land borders are prone to 'unofficial fees' and stricter scrutiny regarding how you support yourself.