I read that too on the koh tao community fb page.
I'm thinking a few things:
1.There are many people who have an intense "party" lifestyle on these islands-alcohol, acid etc and there are certainly casualties of heavy drug use who haven't fully recovered from strong "trips" they've taken. These places also attract people escaping from various things.In short, plenty of untrustworthy spaced out characters. That's why I don't think, If SM was a bit this way inclined, that it implicitly indicates he was involved in the crime or that he is lying. He is one of many party heads of which many are not very "healthy or well functioning" contextually in that sort of place.
2. I find it feasible that losing a close friend in such a brutal way on your own doorstep could easily induce extreme paranoia. This also does not mean what he has said is untrue. He may be in a state of shock and trauma. If he was very very drunk last night as some on the koh tao fb forum have said he was. This also does not mean what he says is a lie.
I can imagine myself freaking out completely and feeling/believing noone and nowhere is safe in a situation such as this , on a remote island after a brutal murder.. What would a "normal reaction" to an event like this be??? Is there such a thing?
3. I have read that he was a very close friend of DM. I read they lived together whilst at university.
4.I also read that although SM had only been on koh tao for a week and a half or two weeks max he had previously lived and worked there for 18 months.
5. Is it possible that the guys who accosted him genuinely were wondering if he was guilty and were planning some vigilante action?
I'm interested to know what occurs over the next few days, am hoping SM makes it safely out of thailand and that justice is served and the truth discovered.
I've never been to Thailand and wouldn't dare to post on some of the sites that people have cited, but I've never been judged for expressing my opinion here

eace: ! Having read the posts on the Koh Tao FB page, Thai Visa and local news sites, I agree it looks like SM is freaking out (even if he didn't know David, it's a pretty horrific thing to be caught up in, regardless of how "psychologically stable" you may be). - by his own admission, he got drunk; sounds like he then mouthed off about his feelings/theories - possibly throwing out a few wild accusations - which has riled the local expat community (assuming they're not 'in' with the mafia). And now he's terrified of retribution. He's not responsible for what happened to Hannah - he may have witnessed something or just become extremely paranoid, but even if he's lying about this, his DNA has cleared him.
Given the backlash from people on the island, I thought he might just be a media hungry fantasist, but when I read into it, it sounds like he was genuinely scared (he called his mother, girlfriend, Thai police and the British Embassy - although who has their number on speed dial??).
Someone posted earlier that it's interesting that a number of Western news outlets have picked this up but not Thai (this may have changed) - I agree, but it could also be Western journalists clutching at anything they have because the Thai police are not being very forthcoming...
Sorry if this has been posted previously, but is there a link indicating that SM was a friend of DM at uni?