Is it possible to convert the category of land use? Any charge incur?

Yes, it is possible. Applications have to be submitted to land and mines offices for such conversion to be carried out and will be forwarded to EXCO or Jawatankuasa Kerja Tertinggi Kebangsaan (JKKT) for approval.

There will be a set of standard documents to be furnished to the land offices as per their requirement, you should contact the corresponding land offices to get a checklist of documents to be furnished
ie. Requirement of Pejabat Tanah dan Galian Selangor

Upon conversion approval, conversion premium will be charged and the amount is differ from case to case basis.

Simple rule of thumb is, the premium is calculated based on a percentage of newly converted land value which determined by Valuation And Property Services Department (Jabatan Penilaian dan Perkhidmatan Harta, http://www.jpph.gov.my). Percentage charged might differ across offices, switching between categories, or it might be just a nominal charge if such conversion fall under certain categories.

For instance,
Melaka Tengah District Land Office - percentage used is stated within Kaedah Tanah Melaka (Pindaan) 2001. They do provide an online version of premium calculator.

OFFICE OF THE LAND AND MINERAL SELANGOR - percentage used is stated within Kaedah Tanah Selangor (Pindaan) 2003.

For exact percentage or nominal charges that imposed on individual case, it is advise to acquire direct consultation from individual land offices.