using System;

using System.Text.RegularExpressions;

using System.Linq;

using System.Diagnostics;

public class Program

{

    private static readonly Regex cjkCharRegex = new Regex(@"\p{IsThai}");

    public static bool IsThai(char c)

    {

        return cjkCharRegex.IsMatch(c.ToString());

    }

    public static void Main()

    {

        var regex = new Regex("([\u0E00-\u0E7F])");

        var stopWatch = new Stopwatch();

        stopWatch.Start();

        Console.WriteLine(regex.IsMatch("กรุงเทพมหานคร"));

        stopWatch.Stop();

        Console.WriteLine(stopWatch.Elapsed.TotalMilliseconds + "ms");

        char[] sometext = "กรุงเทพมหานคร".ToCharArray();

        if (sometext.All(z => IsThai(z))) Console.WriteLine("true");

    }

}