public partial class Form1 : Form
    {
        private readonly SynchronizationContext _cont;
        public Form1()
        {
            InitializeComponent();
            _cont = SynchronizationContext.Current;
        }
        private void button1_Click_1(object sender, EventArgs e)
        {
            new Thread(() => button1.Invoke(new MethodInvoker(delegate { button1.Text = "ablala"; }))).Start();//1 способ
            new Thread(() => _cont.Post(delegate(Object o) { button1.Text = (string) o; }, "blablabla")).Start(); // 2 способ 
        }
    }