Yes, two refs in the ring was the original way and many bouts still have them. So its not lost and you will see it. In recent years, in the bigger stadiums, they shifted to one and its more common now. But outside of those type of big fights, there are two refs. In ancient times or before the suppression, even in thailand, they werent really refs in olden times, they were reps for each fighter to maintain order and to move in if they guy gave up. They continued with two in Burma making them into refs as time went on. If I remember correctly in the older burma vs thailand fights, there had one ref for the burmese fighter and one for the thai. But now they have one ref.
3 chances remains but plays out more like in boxing, but 3 kos I havent seen much outside of the old format fights like in the makeshift rings or in the sand. The 3 knockout rule obviously turned into second chance in the modern era but again not always in play. Phil Dunlap mentions this on his tape and he is correct because that was at one point the main determining rule of original lethwei. There is diversity in what type of lethwei match up its going to be and how it will be fought. Something I like alot about the sport personally. By the way, there was an issued organized and unified rule book for Lethwei. It was given to me in burma and I believe there was a translation or pieces of it translated on the web. I seem to remember it came from Phil or Phil posted it. I will have to check on that. You can consult that as well for a further more concise understanding. I have my translations and notes on it but its not with me right now so I am pulling from memory, so i could be off a bit. All the info everyone contributed here is correct to the best of my knowledge.
I think when people go to Burma and see the fights, they will generally see them in the big arenas in Yangon and Mandalay. So they will see one ref, the ref if its not a second chance, acting a big more quickly like a ref in any modern sporting event like muay thai or boxing. There are second chance rules for some matches so suddenly you might be shocked to see a guy dragged to his corner and revived and sent back out to fight. Refs whether one or two will stop lopsided fights in the ring. Fighters can also be disqualified even for a fight sport with little rules.
Now also you will see weight classes. In the old rules, it was just match ups, sometimes a visual or two people just agreeing to fight, or a head man would chose the people that fought. This is type of organizing the fight was done everywhere from India to Thailand, Laos, Cambodia, etc(where you see them matching fights by visual, and I actually show the correlation of that briefly between the burmese match ups from southern burma and the kushti event in delhi in the physical body 2 dvd). But the old ways of just creating match ups or letting two people who want to continues on outside of the big events. So it remains an active component.
Something I really love about modern Lethwei is that they usually start with three round fights, four round fights then the main five round fights. Since there is no amateur fighting in lethwei. This was a great way to start your fighting career, usually if a foreigner wants to go in I tell him to do a 3 rounder to get the feel for it. Its a great way to grow into the sport when they feel you are ready they advance you to the four rounder then to the five rounders. This is more modern in the advent of the rounds being used in Lethwei but one of the better additions for the sport.
One other thing I would like to mention. There are no decisions or judges in lethwei in any bout I ever seen. Its win, lose or a draw.
They do something because of it(having no judges and point deductions)and one tactic is to drop down to the ground to stop the action. If a fighters back hits the ground more preciously two shoulders from a throw, punch, etc, there is a stop of the action. In one bout I saw, the lightweight title holder was losing badly, i meaning his face was a mess, in desperation he threw his opponent beautifully and landed him on his back, his opponents shoulders and back cleanly hitting the ground, then followed with one of the best short spinning elbows i had ever seen, knocking the guy out.
The crowd was silent. The ref pulled the lightweight champ off the guy and instead of raising his hand, disqualified him. I had to watch the footage back with the promoter for him to break this down. Everyone in the crowd just shook their heads and quietly left since it was the main event. It was a clear foul and the ref was on it and the crowd understood. There were no protests.
There is a lot of different ways Lethwei can be fought from the old original way all the way across the big arena bouts fought with a bit more modern flair, but it remains Lethwei, those guys are the last of the true bare knuckle fighters in the region. Its a genuine link to the past.