Need some answers on the following.

The lawn at the back now has maybe 2 inches of brown grass with an inch or so of green on top. Gets no traffic human or dog.

One guy says now, rainy season, is a good time to cut right back v short and get rid of the brown base and should do every 3 or 4 years.

Another says just cut back a little bit, not short.

Help.

 

Not enough information.  What kind of grass? How often to you mow routinely? Do you irrigate? How often? Do you fertilize? With what?

I suspect that the brown under belly is due to not mowing frequently enough so that the lower part of the grass blades don' t get sun.  And maybe the grass is starved for balanced nutrition and can only green the tops.  

 

I mow my Malaysian grass every week during the growing season and as needed during the winter months when growth is slower. I mow it at about 3 inches without a catcher and let the cut grass infiltrate to build soil organic matter.  I irrigate based on perceived need when it doesn't rain, and I fertilize monthly or six weeks.  There is no brown under-layer, it's all green. 

 

If you decide to scalp it to expose the lower brown layer, now would be the time to do it during growing season when it can get rain watered and respond with new growth,  When you do it, fertilize moderately so that the new growth is well nourished. Then mow frequently so that you don't have to take off more than a third of the blade with each mowing. 

 

The ground rule (non-tropical countries) is to not remove more than one third of the height at a cut. If you do, the lawn won't die but it will look like a dog's dinner. As Dr Treelove says, now is a good time to do it, maybe accompanied by a distribution of fertiliser a few days after cutting.

Grass always comes back in thailand....i cut it very short and accidently totally off but it always came back.