Was only there for 2 days but quickly worked out the best (for me anyway) was bus and grab car. I avoided grab bike though as seemed too dangerous (most passengers riding without a helmet and drivers weaving in and out of heavy traffic). Avoided the Tuk Tuk's. Prices are inflated for eg one guy wanted 300 baht for what cost me the previous day 120 Baht in a grab car. Also a Tuk Tuk driver offered me quite a reasonable price one time (40 Baht) but after I accepted he proceeded to tell me that we need to make a stop at a tailors store so he can get a fuel voucher ("no need to buy clothes, just look is good for me"). I told him no and caught the bus for 13 Baht to Phaya Thai train station. I didn't bother with taxis. I have trust issues at the best of times so prefer to keep my anxiety levels to a minimum 
What struck me the most though is the Tuk Tuk driver could have made some easy money (possibly half his fuel for the day) but let it slide. What would be great though is if they put a Tuk Tuk option on Grab.
