To be honest, I never had a Real helmet, and it's therefor difficult to comment on the quality. For safety standards, according to some the DOT standard is relative easy to obtain, it's much more difficult to get a ECE or Snell M2005 standard approval.
And if you think that the 3 (DOT, Snell and ECE) are the only motorcycle helmet standards... You have; ACU (Auto-Cycle Union) Gold or Silver badge, AS/NZS 1698:2006 (Australia and New Zealand), BSI (British Standards Institute) 6658, CSA CAN3-D230-M85 (Canada. they no longer certify motorcycle helmets), DOT FMVSS 218 (USA), GOST R 41.22-2001 (ГОСТ Р 41.22-2001) (Russia) (based on ECE 22.05), NBR 7471 (Brazil), IS 4151 (India), JIS T 8133:2000 (Japan), Snell M 2005 "2005 Helmet Standard For Use in Motorcycling”, SNI (Indonesia), SHARP (UK) - Star Rating, CRASH (Australia) - Star Rating, ECE Regulation 22 (Europe) (2001), and the TCVN 5756:2001 (test and certify by QUATEST 3) (Vietnam).
With Real Helmets I cannot understand why they applied for DOT approval, and not for SNI (Indonesia), Star Rating (Australia), IS 4151 (India) and TCVN 5756:2001 for Vietnam. This 4 motorcycle helmets approval standards would make more 'business' sense, free-trade-agreements. But some of this standards are remarkable less easy to obtain than the DOT standard... I have no idea if Real Helmets are available in the USA, I cannot find anything on Internet what suggests they do...
Thai manufactured helmets are they bad? No I not think so, but when I do some shopping in our neighborhood I wear a simple helmet (Index +/-3,000 THB I believe), if I really need to go somewhere I wear my 'better' helmet (which was +- 19,000 THB ).
Helmet sizes, I know that Index makes XXL helmets not sure about Real Helmets (probably also), most of the time you probably need to ask if they can order one. Not much Thai's with bigger heads around and helmets have an expiry date...