are there tools to measure the exact download speed of servers ?

when I initially got 3BB, my download speed for a file is 600KB/sec; lately the speed is only 120KB/sec;

is the server restricting the speed of downloads ?

Welcome to Thailand and Thai broadband. No matter which provider you choose some days you will be happy but more often than not you will be moaning about the slow speeds. Just get used to it. Speed depends on so many variables etc. How many people are using it at once, the distance from the exchange,where in Thailand you are, what you are trying to download etc. You can use any of the free download speed testers and get a different speed every time. Learn the mai pen rai mentality and if today its crap then maybe tomorrow it will be better

To be honest True has got its act together never really had a bad day on 16mb Premium and now on 50mb VDSL2 with them and again never had a bad day speed wise.

Don't believe the hype, I've used True & TOT both get now where near the advertised speeds, the phrase ' up to ' has a lot to answer for...

Try DuMeter for continuous monitoring and day/week/month totals.

Speedtest Bangkok: http://bangkok.speedtest.thaivisa.com

Speedtest Singapore: http://speedtest.thaivisa.com

Bandwidth Diagnostics (ff add-on)

Minimeter 1.1.2.0 (ff add-on)

NetLimiter (internet traffic control)

NetMeter

NetWorx (usage monitoring)

Ookla (line quality test)

Ookla Blog (broadband speed info)

Oz Broadband Speed Test

Pingtest (broadband speed test)

Softpedia - Bandwidth Tools

Speedtest (broadband speed test)

TechsupportAlert - Reviews

Telenet (broadband speed test)