diff --git a/index.d.ts b/index.d.ts
index 13b1fea..260c1ce 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -6,4 +6,4 @@ export interface Window {
 
 export as namespace isValidThaiID;
 export { isValidThaiID };
-export default isValidThaiID;
\ No newline at end of file
+export default isValidThaiID;
diff --git a/src/validator.ts b/src/validator.ts
index c401e4e..94d0677 100644
--- a/src/validator.ts
+++ b/src/validator.ts
@@ -5,39 +5,60 @@
 
 /**
  * Validate the Thai citizen ID.
- * @param id The ID to validate.
+ * 
+ * This function validates a Thai citizen ID by checking its format and calculating the checksum.
+ * The ID must be a string of 13 digits. If the ID is provided as a number, it will be converted to a string.
+ * 
+ * @param {string | number} id - The ID to validate. It can be a string or a number.
+ * @returns {boolean} - Returns true if the ID is valid, otherwise false.
+ * 
+ * @example
+ * // Valid ID
+ * const isValid = isValidThaiID('1112034563562'); // true
+ * 
+ * @example
+ * // Invalid ID (wrong pattern)
+ * const isValid = isValidThaiID('1101700230705'); // false
+ * 
+ * @example
+ * // Invalid ID (less than 13 characters)
+ * const isValid = isValidThaiID('110170023073'); // false
+ * 
+ * @example
+ * // Invalid ID (mixed characters)
+ * const isValid = isValidThaiID('11017002070d3'); // false
  */
 function isValidThaiID(id: string | number): boolean {
   // Convert number to string if the ID is a number.
   if (typeof id === 'number') {
-    id = id.toString()
+    id = id.toString();
   }
   // Check if the ID is a valid string of 13 digits.
   if (!/^\d{13}$/.test(id)) {
-    return false
+    return false;
   }
 
   // Calculate the check sum.
-  let sum = 0
+  let sum = 0;
   for (let i = 0; i < 12; i++) {
-    sum += Number(id[i]) * (13 - i)
+    sum += Number(id[i]) * (13 - i);
   }
-  const checkSum = (11 - (sum % 11)) % 10
+  const checkSum = (11 - (sum % 11)) % 10;
 
   // Check if the check sum is equal to the last digit of the ID.
-  return checkSum === Number(id[12])
+  return checkSum === Number(id[12]);
 }
 
 // Export the function.
 if (typeof module !== 'undefined' && typeof module.exports !== 'undefined' || window === undefined) {
-  module.exports = isValidThaiID
-  exports.default = isValidThaiID
-  exports.isValidThaiID = isValidThaiID
+  module.exports = isValidThaiID;
+  exports.default = isValidThaiID;
+  exports.isValidThaiID = isValidThaiID;
 } else if (typeof window !== 'undefined') {
   // Support legacy version of the browser.
   // @ts-ignore
-  window.isValidThaiID = isValidThaiID
+  window.isValidThaiID = isValidThaiID;
 } else {
   // @ts-ignore
-  global.isValidThaiID = isValidThaiID
+  global.isValidThaiID = isValidThaiID;
 }