Raster SDK API documentation and sample codes are present in the MapInfoPro installation directory at the following path.C:\Program Files\MapInfo\Professional\Raster\Documentation\API\.
The 'MapInfoProRaster.NET_SDK.chm' file at this path contains the API documentation and the Sample Code folder contains the samples in C#.The samples does not contain mapbasic integration code as it is. But we can provide it based on the specific usecase.
RasterSDK API has more granular level customization option for different operation. Because of this it exposes more parameters for the callers to configure. These parameters can be constructed easily in .Net.The contouring task you are trying to run here can make use of the API RasterAnalysis.ClassifiedPolygonContour( ...) method.Since you wish to call this method from MapBasic, the easiest way is to create a .Net library ,say RasterMapBasicInterface.dll, that consumes raster Raster SDK API . We can set all relevant paramters in the RasterMapBasicInterface and call RasterAnalysis.ClassifiedPolygonContour( ...) method from inside RasterMapBasicInterface.On the Mapbasic side we can import methods of RasterMapBasicInterface and call them easily.I have attached the .Net interface dll and the MapBasic script here.Also attached the C# source code for reference.Any customization in the parameters passed can be done in the .Net Interface class .