这个随意都行吧，比如用接口自带的一个方法
var
Task: ITask;
procedure TForm1.Button1Click(Sender: TObject);
begin
Task := TTask.Create(
procedure()
begin
while True do
begin
try
Task.CheckCanceled; // 当调用Cancel后该过程会触发一个异常，只须捕捉该异常进行处理
except
Break;
end;
Edit1.Text := DateTimeToStr(Now);
end;
end);
Task.Start;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
Task.Cancel;
end;

或者用什么其他设施也一样：
const
FormClosing = -1;
procedure TForm1.Button1Click(Sender: TObject);
var
Task: ITask;
begin
Task := TTask.Create(
procedure()
begin
while True do
begin
if Self.Tag = FormClosing then
Break;
Edit1.Text := DateTimeToStr(Now);
end;
end);
Task.Start;
end;
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
Self.Tag := FormClosing;
end;

接着上楼的加点你后来提到的：
type
TForm1 = class(TForm)
Button1: TButton;
Edit1: TEdit;
Button2: TButton;
procedure Button1Click(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
procedure Button2Click(Sender: TObject)
publi
procedure DoSomething;
end;
var
Form1: TForm1;
implementation
uses System.Threading;
{$R *.dfm}
const
FormClosing = 1;
procedure TForm1.Button1Click(Sender: TObject);
var
Task: ITask;
begin
ShowMessage(TThread.Current.ThreadID.ToString);
Task := TTask.Create(
procedure()
begin
try
while True do
begin
if Self.Tag = FormClosing then
Break;
Edit1.Text := TThread.Current.ThreadID.ToString;
end;
finally
TThread.Synchronize(nil, procedure begin Form1.DoSomething end);
end;
end);
Task.Start;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
Self.Tag := FormClosing;
end;
procedure TForm1.DoSomething;
begin
ShowMessage(TThread.Current.ThreadID.ToString);
end;