I have a '83 honda VF750F Interceptor that has had an overheateing problem for approximately 10 years. While moving, the coolant temperature reads approximately 15 percent on the gauge, which is normal. In stop-and-go traffic, it shoots up to about the 85 percent mark and kicks on the ventilators. I have had both radiators cleaned out, at which time the serviceman said they were in great shape considering how old they were.

He also said they came in about 25 percent clogged. I have replaced the thermostat, water pump, hoses, temperature sensor, radiator and cap over the past year. I'm also running the best coolant money can buy and make sure that no air bubbles are in the system. I would expect the motorcycle to run warmer in Thai heat, but I don't ride when it's so hot. This still happening when the temperature in Thailand dip down to around 25c degrees.

Hello, sounds like you have done all the correct things, flushing, replacing parts, using good quality coolant.
In my uneducated opinion, seeing your cooling system is in top order, this running hot in heavy stop/start traffic is completely normal. These bikes are not designed for big city heavy traffic like the small Thai underbone type bikes are.
Back home in South West Western Australia i have a 2008 Honda Hornet 600cc with less than 1500km on the clock, when im doing similar riding in busy traffic jam conditions the digital temperature guage rises from a normal 85 degree celcius to high 90s on occasions ive seen it read above 103 degrees celcius. As the bike is practically brand new, It must be because of the lack of airflow thru the radiator. Once i get back up to 60km/h or more, after a few minutes the temperature readout starts to steadily drop returning to normal running temperature.
Altho the ambient temperature ( on the weather report ) may say its 25deg , the actual temperature in heavy traffic on bitumen roads in a concrete jungle with SFA ( sweet fu.. all ) breeze will be considerably higher.
I also have an Aussie classic car (EH Holden) with a 350 Chev V8 which used to do exactly the same thing, even worse when stuck in freeway traffic jams or idling for more than 10 or so minutes. I purchased a custom enlarged 4 core radiator specifically designed for my vehicle/engine combination to stop this problem happening but it did not improve things much at all.
So then i decided to purchase 2 CraigDavies electric thermatic fans and installed them infront of the radiator blowing air thru it, This has solved my overheating problem totally. I even removed the origional fan belt driven fan with no increase in engine running temperature.
Can i suggest that you remove the temperature switch that activates your fan at high temperatures and wire it direct so the fan is always running when the engine is running. Or if possible, fit the biggest thermo fan ( or 2 fans if they will cover more surface area of your radiator than 1 large thermo fan ) that you can fit to your radiator. Im not familiar with your model of bike so not sure of the fan its running as standard, but you definately need more airflow thru the radiator to reduce your bike overheating in hot low speed conditions.

Maybe someone has some other suggestions, but the above info is from my direct experience, hope this helps you out.
Cheers and good luck.
Matt.
P.S. Where is all the good New Years Eve partys in Bangkok ?????

Since you and the motorcycle have been sweating it our for so long, it's probably nothing to worry about. Honda V4 engines tend to run a bit hot by nature, but not when it's about 25c degree outside. Especially considering you've exercised due-diligence in terms of cooling-system care. We asked a Honda big bike expert...

And he said 'We have had some radiators clogged up, so some sort of blockage that's still in there would be my first thought as long as the fans are coming on,' And the instrument itself or its sending unit could be bad.'

The next step is to aim a remote-sensing infrared thermometer at the radiator – the same sort of thing used to diagnose air-conditioning systems – to see how hot they really are. 'That way he can tell if the engine is really running hot, I mean anything over 110 degree Celsius.'

If the temp gauge and sending unit check out and the engine really is running that hot at 25c degree weather, have another look at the radiator...