[quote user="Raja Damirekula"] In which logic built in thinning tool is developed in MicroStation[/quote]
You've been advised elsewhere to post your question to this Forum because Bentley's GIS products include the functionality you want.
Those applications use MicroStation as the base platform. MicroStation, as you have discovered, does not have a line thinning tool. Starting with MicroStation GeoGraphics, nearly two decades ago, to Bentley Map today, those GIS products have included geometry rectification tools, which include line thinning.
If you install, for example, Bentley Map, you will have the functionality you want. Additionally the Bentley Map SDK provides programmatic access to a library of GIS functions. However, you must install the Bentley application in order to use its SDK. You can't use, say, the Bentley Map SDK independently of Bentley Map.